1. Field of the Invention
The present invention relates to equipment for separating the wort from the spent grains, and more specifically to a filter-press for separating the mash. Most efficiently this invention can be used in brewing.
When improving the existing or designing new mash-separating equipment efforts are made to decrease the duration of the process of separating the wort from undermodified malt grain and remove as much as possible of soluble extracts from the spent grains. However, this urgent problem still remains to be solved, which is evidenced by the fact that the separation of the mash by the existing equipment takes from 1.5 to 2 times more time than the preparation of the mash. This disproportion can be eliminated in the existing apparatus either by increasing the filtering area, through increasing the size of the separating means or at the expense of incomplete extraction of the soluble extracts, which cannot be considered as an adequate solution of the problem.
2. Prior Art
Until the present time most breweries have made use of filter vats (cf. for instance, Nazarov i dr., Technologiya i oborudobanie pistchevyh priozvodstv, "Pistchevaya promyshlennost", M., 1977 p. 249) made in the form of a hollow cylinder having a bottom with openings and a level sieve placed thereover. Communicated with these openings are pipes for withdrawal of the wort. The mash is fed into the filtering vat so that the layer of spent grains on the sieve is from 30 to 45 cm thick. In case the depth of this layer is greater than indicated one, the filtration proceeds much slower and the spent grains are inadequately leached. If the depth of the layer of the spent grains is below the indicated value, this layer will not serve as a filter bed, which results in a poor filtration and the wort gets hazy as a result of that small particles of the coarsely ground malt get thereinto.
Therefore the filter vats generally have a height of not more than 2 m, and a diameter from 3 to 6 m. They take a great deal of room but have a rather low efficiency. This efficiency can be improved only at the expense of a larger size of such vats (namely their diameters). The filtering area of the filter vats have been considerably increased by the introduction of additional vertical sieves (cf. USSR Inventor's Certificate No. 392,088; Veselov I. Y. and Tchumasova M. A. Technologiya piva, "Pishchepromizdat," M. 1963, p. 262), which, however affected the quality of the wort. This is explained by that the sieves do not practically trap small particles which, as a result, get into the wort. To separate these particles it is necessary to form a filter bed of spent grains, which filter bed cannot be formed on the vertical sieves. Therefore, filtering through the sieve portions located above the filter bed surface is unwanted since it may cause turbidity of the wort.
Attempts have been made to use for separating the mash the drum suction filters (cf. FRG Pat. No. 1,254,566). It was believed that the drum suction filter would promote intensification of the separation process. This equipment, however, has not found wide application in brewing, which is explained by the fact that frequent chocking up of the filtering material and insufficient leaching, of spent grains.
There has been also a trend to effect separating of mash by means of filtering and settling centrifuges (cf. FRG Pat. No. 1,067,395). However, attempts to obtain a bright wort by centrifugal separation have not been successful so far. It is worth noting that recently many modern breweries (Tuborg in Denmark and others) have been again equipped during their reconstruction with filter vats.
Along with the above-mentioned equipment extensive use has been made recently of filter-presses (cf. for instance, Veselov I. Y. i Tchumakova M. A. Tehnologiya piva, "Pishchepromizdat," M., 1963, p. 267-270). A filter-press of this type comprises a base having vertical supports carrying horizontal guides secured thereto. Mounted on the horizontal guides are vertically positioned filter plates and frames. Between each filter plate and the frame adjacent thereto are disposed filter blankets made from a filter cloth. Each filter plate has one corrugated surface whereupon the filter blankets are placed. The frame cavities are communicated with a mash supply collector. The corrugation flutes form vertical ducts communicated with a wort withdrawal collector. The filter-press is also fitted with a hydraulic means for tightening the filter plates and frames to form a filter stack, as well as a means for supplying and withdrawing sparge water. When the mash is passed into the cavities of the filter frames the malt grains and coagulate settle down on the filter blankets to form a 6-7 cm bed. The wort is passed through the bed of malt grains and filter cloth to the vertical ducts formed by the flutes and then withdrawn through the collector. After the filtration of the first wort is completed the malt grains are subjected to the leaching which is effected by supplying the sparge water to the ducts in the filter plates, which sparge water being heated to a temperature of 78.degree.-80.degree.. The wort passing through the bed of malt grains and the cloth of the blankets gets into the vertical ducts and then is withdrawn through the collector. The sparge water, while passing through the bed of the malt grains and the blankets, washes out soluble extracts and then is added back to the first filtered wort. The leaching process is kept running until the density of the sparge water is lowered to a required value. Thereafter, the filter plates and frames are drawn apart by moving them by hand along the horizontal guides. The filter blankets are removed through the openings formed between the frames and plates after the latter have been drawn apart. The cavities of the filter frame are cleaned from the spent grains and the filter cloth of the blankets is washed to remove the dregs.
The advantage of the above filter-press over the filter vats lies in that having a much smaller cross section as compared with the latter it provides for a higher efficiency due to the fact that it has a larger filtering area. In addition, a filter-press permits processing more finely ground malt, thereby making it possible to increase a yield of the extract, and to utilize a greater amount of non-malt materials which affect filtration process in the filter vats.
Nevertheless, operating such filter-presses is associated with a number of difficulties. In particular heavy cast-iron plates and frames are handled by hand. Besides, cleaning of the frame cavities and replacing of a great number of the filter blankets take too much time.
There is known a filter-press wherein all these operations are mechanized (ref. Chernobylskiy I. I. i dr. Mashiny i apparaty khimicheskih proizvodstv, "Mashinostroenie," Moskva, 1975, pp. 44-46). This filter-press comprises a framework having vertical guides. Mounted in a horizontal position on the upper ends of the guides is a thrust plate. On the same guides is secured in a horizontal position a movable pressure platen connected with a reciprocating drive. Between the thrust plate and the pressure platen on the vertical guides are also positioned filter plates. These filter plates are mounted horizontally above each other. Each filter plate has side boards and a horizontal partition fixed to the lower butt ends of said side boards, whereas fixed to the upper butt ends of the side boards is a sieve. Thus, said side boards, the horizontal partition and the sieve define an inner space of the filter plate. On the vertical guides between the filter plates are also installed in a horizontal position frames. Between the filter plates and the frames is passed in zigzags an endless filter band. Each loop, of the filter band is passed round the frame and the filter plate located thereabove. The endless filter band is connected with a stepping drive and runs through a cleaning chamber. Communicated with the cavities of the frames is a mash supply collector, whereas connected with the cavities of the filter plates is a wort withdrawal collector. The filter-press also includes a means for delivering and withdrawing sparge water. This means includes a valve box having valves to cut off the mash supply and let the sparge water pass to the frame cavities. The sparge water containing the extract of the molt grain is withdrawn from the filter frame cavities through the wort withdrawal collector. In the upper part of each frame there is located a membrane for pressing the settling.
It is quite obvious that the above-filter-press has a number of advantages over the aforecited appraratus, which advantages are the following: first, displacing and tightening the filter plates and the frames are effected by a special reciprocating drive; second, replacing the filtering cloth and removing the dregs are done by moving the endless filter band driven by a stepping drive; third, the dregs settle down by gravity, since the frames are oriented horizontally. All these factors provide for a higher efficiency of the filter-press. Nevertheless, in practice, operating this filter-press was associated with a number of difficulties. It has been established, for instance, that the sparge water at the first stage of the leaching process locally washes off the malt grain bed, which results in that the sparge water passes through the washout zones without removing the extract from the larger part of the malt grains. Furthermore, pressing the malt grains by the membrane results in that a great deal of suspended particles get into the wort. Attempts to eliminate these disadvantages have not yielded appreciable results, which is responsible for that the above filter-press has not gained wide application in brewing.